sub-adult (4⁺ cy): January - April

Sub-adult LBBG in 4cy and 5cy very much resemble birds in adult plumage. On average, 4cy birds may still show a few immature features, but on the other hand some 4cy match the average adult very well and may be difficult to identify. 

Only very few sub-adults remain in the Netherlands during the first three months of the year. Together with adults, sub-adults return to the colonies in spring and maybe a few will already breed. It's difficult to separate sub-adults from adults, although sub-adults normally show:
- some black on the bill
- pale yellow legs
- or no pure yellow irises.
However, this may occur in adults in winter plumage as well.

Best features to distinguish sub-adults from adults are:

- less developed primary tips,

- less developed primary mirrors (but beware of smaller sized mirrors in females, normally only showing a P10 mirror),

- extensive black on the bill,

- extensive wear in the coverts with a brown hue, already early in spring and sometimes a hint of barring.

 

	Car acccident sub-adult LBBG in the colony. Died today. Check this web page to get an idea of grey-tone, bare parts coloration and pattern on tail, secondaries and primaries. Bottom image: a fresh 4cy LBBG, with black in the tail and on all secondaries.